London: Britain`s police watchdog on Wednesday found no evidence of wrongdoing by officers involved in the shooting of a mixed-race man in London in 2011, which sparked nationwide riots.

Mark Duggan, 29, was shot twice after police stopped the taxi he was travelling in through Tottenham, north London, as part of a pre-planned operation against gang crime.

After an investigation lasting three and a half years, the Independent Police Complaints Commission (IPCC) accepted the assertion by the officer who shot him that he thought Duggan was armed.

However, IPCC deputy chairwoman Rachel Cerfontyne said the lack of audio or video material made it impossible to know exactly what happened that August day.

She called on police to urgently come up with proposals to ensure that vehicles used in undercover armed operations were fitted with audio and visual recording devices, and that all radio communications were recorded.

"If implemented, my recommendations would not only shorten the investigative process, they would provide investigators with immediate, accurate and incontrovertible evidence, which would be of benefit to all," she said.

Duggan`s death kicked off riots in Tottenham, an ethnically diverse urban area, which subsequently spread across London and to other cities including Birmingham and Manchester, leaving five people dead and causing huge damage to property.

A formal inquest into the shooting found last year that Duggan had been lawfully killed, although the jury concluded that he did not have a gun in his hand when he was shot.

Instead, jurors found the father-of-six had thrown the gun he had been carrying in the taxi onto some nearby grass.

The IPCC report found "no credible evidence" of claims that the gun had been planted or thrown there by police.